I have the same problem. The noise has something to do with the light switch. Try putting ur ear right up against the radio/ centre console with the light switch turned off; you'll hear no buzzing noise. However, when u flick the light switch on, the buzzing noise will appear. It is a faint buzzing noise, it comes from behind the centre console and not dash. Also, it happens when the engine is both on and off. The noise is still there as long as that light switch is on.

I went to the bmw dealership and thought it was the radio's problem. They swapped in a new radio, but unfortuneately that wasn't the case. The faint buzzing noise is still there. I got them to re-check the radio unit to see if any pins were loose, but none were. The shop foreman said he heard the noise on other bmw models too and said it is normal.

All in all, they didn't fix the problem, but said it's normal? What do you guys think? It seems like we all got the same problem and no one can solve the mystery of this buzzing/humming noise.

I heard from others it could be some electrical interference from a poorly shielded wire or a high current wire that is close to the front centre speaker wires. Or it might be the electrical fan from the ecu box. Any thoughts?

Sounds like RF interference, likely from a voltage transformer stage.
Halogen lamps are infamous for this, unless shielded properly. If you have a portable radio you can likely pinpoint the source by moving the antenna around from several different positions, and triangulate.

Sounds like RF interference, likely from a voltage transformer stage.
Halogen lamps are infamous for this, unless shielded properly. If you have a portable radio you can likely pinpoint the source by moving the antenna around from several different positions, and triangulate.

Speak of halogen lamps. I just got my daytime running lights replaced recently as one of the light burnt out. My car is still under warranty so I took it to bmw. Maybe the guy that replaced the bulb didn't do it properly?

So if I were to switch the original halogen daytime running lights to xenons, it won't make the buzzing sound no more?

I have the halogens. Yes, the noise persists even when the engine is switched off. In fact, the faint noise is there whenever I sit in the cabin. I have no idea whether is actually goes away when I leave the cabin...It's like a ghost.

The noise becomes louder when the front headlight is turned on. The noise will be at its peak when I play iPhone music through AUX (not the iPod connection thingy)

My recommendation: Wind the power wire to the stereo through a ferrite bead a couple of times (at the stereo end of the wire). Or ask your mechanic if he can do it. It won't hurt, and has a very good chance of reducing RF induced noise, which this almost certainly is.

I went to another bmw dealership and have them look at the buzzing problem again. They said it's normal. Bmw has a bulletin out for this problem. "Characteristic of the audio system D6513-00000000-01-901. This is normal as per test plan."